1. Field of the Invention
The present invention relates to a method for producing an L-amino acid using a microorganism, and especially relates to a method for producing L-amino acids such as L-lysine, L-threonine, and L-glutamic acid. For example, L-lysine and L-threonine are industrially useful as additives for animal feed, ingredients in health foods, amino acid infusions, and so forth, and L-glutamic acid is useful as a seasoning.
2. Brief Description of the Related Art
L-amino acids are industrially produced by fermentation using microorganisms belonging to the genera Brevibacterium, Corynebacterium, Escherichia, and the like. For example, methods for producing L-lysine include those disclosed in European Patent No. 0643135, European Patent No. 0733712, European Patent Publication No. 1477565, European Patent Publication No. 0796912, European Patent Publication No. 0837134, International Patent Publication WO01/53459, European Patent Publication No. 1170376, and International Patent Publication WO2005/010175.
In such methods, strains isolated from the nature or artificially produced variant strains are used. Furthermore, microorganisms which have been modified by recombinant DNA techniques to increase the activities of enzymes involved in basic L-amino acid biosynthesis, and so forth are used.
Orotate phosphoribosyltransferase [EC:2.4.2.102.10] is an enzyme of the pyrimidine biosynthesis system, and is encoded by the pyrE gene. The pyrE gene is present on an operon with rph, which encodes RNase PH. The rph gene is located upstream relative to the pyrE gene. In the Escherichia coli MG1655 or W3110 strain, the coding region of the rph contains a −1 frameshift in the 3′ end region, which results in insufficient expression of pyrE and causes pyrimidine starvation (Journal of Bacteriology, vol. 175, June 1993, p 3401-3407).
However, there have been no reports concerning the relationship between the expression of the rph-pyrE operon, the amount of the pyrE gene product which is expressed, orotate phosphoribosyltransferase activity, and substance production by Enterobacteria. 